It is already known to provide the antenna base of the external antenna of a motor vehicle with an antenna connection that is electrically connected to the transmitting and/or receiving part of the antenna and to pass this antenna connection through an orifice provided as a circular hole in the vehicle body, and to attach it, e.g., using threaded connection means to an antenna cable linked to a transmitting and/or receiving unit. To prevent the external antenna from twisting about the axis of the antenna connection, provision is made at the antenna base for an additional plug for locking against rotation, and this plug is passed through a second orifice of the vehicle body provided for this purpose. The two orifices are standardized in many motor vehicles and include two circular holes of different diameters, disposed at a predefined distance from one another. The drawback in this context is that only one antenna connection is able to be passed through the first orifice. If it is required to connect a second transmitting and/or receiving unit via a separate antenna cable to the antenna, then a third orifice must be made available for leading through an additional antenna connection. This is not possible using the standard connections of most automotive manufacturers.